The conventional approach to increase the scan angle of an edge slot array is to use a serpentine type waveguide array. However, the serpentine type of waveguide array uses considerable space for the serpentine. Another approach is to use dielectric loading in the waveguide, which not only increases the array weight but also increases the insertion loss significantly. A longitudinal slot in the broad wall has been used but the broad wall design restricts the scan range (in the plane orthogonal to the waveguide axis).
A unit element of a periodically loaded edge slot array includes a reduced-height waveguide section having top and bottom walls and opposed first and second sidewalls defining a waveguide space. A slot is formed in the first side wall at an angle with respect to a waveguide longitudinal axis. At least one conductive post protrudes from the top wall into the waveguide space. The unit element can be incorporated into sticks of an electronically scanned antenna.